Incandescent light bulbs create light by conducting electricity through a resistive filament, heating the filament to a very high temperature to produce visible light. Incandescent bulbs are made in a wide range of sizes and voltages. The bulbs typically include an enclosure with a tungsten filament inside and a base connector that provides both an electrical and structural support connection. Incandescent bulbs generally mate with a lamp socket having a threaded Edison base connector, bayonet base connector, pin base connector, or any suitable connector for providing electrical power to the bulb. However, incandescent light bulbs are generally inefficient and require frequent replacement. These lamps are in the process of being replaced by more efficient types of electric light such as fluorescent lamps, high-intensity discharge lamps, and, in particular, LED light sources.
LED technology continues to advance resulting in improved efficiencies and lower costs with LED light sources found in lighting applications ranging from small pin point sources to stadium lights. An LED light may be 60-70% more efficient than an incandescent light but may still generate significant amounts of heat. At higher temperatures, light conversion efficiency for an LED light source may drop as power increases, LED life decreases, and light output may be permanently diminished.
While an incandescent light may generate a substantial amount of heat, the heat is generally radiated from the typically free standing filament through the light envelope into the surrounding air. In contrast, an LED light source is generally chip mounted and heat is conducted away through a heat sink. Existing light fixtures are largely adapted to dissipate radiated heat and usually have very little capacity to dissipate conducted heat. In order to reach desired lumen values and maintain compatibility with a significantly large installed base of presently existing fixtures, additional cooling techniques may be required.
Nilssen et al. (US 2011/0193479) discloses an LED lamp that removes heat using evaporation of water or other coolant inside a glass lamp structure. When cold, the coolant pools at the lowest part of the enclosure and a structure may be provided to conduct heat from the LEDs to the coolant or to wick the coolant from the pool to the immediate vicinity of the LEDs. A position switch is provided to ensure that the bulb may only be operated in positions where the structure or wick are in contact with the coolant pool.
Tuma (US 2006/0090881) discloses a device for immersing an electronic component in a cooling fluid. The cooling fluid is disposed within an enclosed volume such that the device is installed over a heat dissipating component and a breachable seal of the enclosed volume is breached, allowing the cooling fluid to contact the heat dissipating component and transfer heat to a sidewall of the device.
Lenk et al. (U.S. Pat. No. 8,638,033) discloses an LED covered with a shell which may or may not contain phosphor for converting the light spectrum emitted by the LED. The shell covered LED is positioned within an outer bulb shell which may also enclose one or more phosphors in a filler material. The filler material may be a thermally conductive fluid, plastic, gel, hydrogel, water, or other material.
Wheelock et al. (U.S. Pat. No. 8,152,341, U.S. Pat. No. 8,277,094, and U.S. Pat. No. 8,562,185) discloses an LED bulb containing a thermally conductive liquid within a shell. A liquid volume compensator is included to compensate for expansion of the thermally conductive liquid. A first volume for the thermally conductive liquid is provided when the compensator is in a first position, and a second volume for the thermally conductive fluid is provided when the compensator is in a second position. It would be advantageous to provide structures and techniques to dissipate heat generated by LED sources that overcome the disadvantages of the prior art solutions.